fix(ingest): race-safe scene_tags insert (ON CONFLICT) — GOON-M

scene_resolver._sync_tags used check-then-insert (select existing -> add if None), which races under concurrent ingest of the same scene: two runs both see existing=None, both add, flush -> IntegrityError pk_scene_tags (Sentry GOON-M, 4 events). Switched to pg_insert(...).on_conflict_do_nothing(index_elements=[scene_id, tag_id]) + in-batch dedup, identical to movie_resolver._sync_tags.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/resolve/scene_resolver.py

@@ -584,18 +584,24 @@ def _sync_tags(
     norm: NormalizedScene,
     source_id: uuid.UUID,
 ) -> None:
+    # PostgreSQL INSERT ... ON CONFLICT DO NOTHING — race-safe. Wcześniejsze
+    # check-then-insert ścigało się przy równoległym ingescie tej samej sceny
+    # (dwa runy widziały existing=None → oba add → IntegrityError pk_scene_tags,
+    # GOON-M). Analogicznie do movie_resolver._sync_tags.
+    from sqlalchemy.dialects.postgresql import insert as pg_insert
+
+    seen_tag_ids: set[uuid.UUID] = set()
     for t_norm in norm.tags:
         tag = resolve_tag(session, norm=t_norm)
-        if tag is None:
+        if tag is None or tag.id in seen_tag_ids:
             continue
-        existing = session.execute(
+        seen_tag_ids.add(tag.id)
-            select(SceneTag).where(
+        stmt = (
-                SceneTag.scene_id == scene_id,
+            pg_insert(SceneTag.__table__)
-                SceneTag.tag_id == tag.id,
+            .values(scene_id=scene_id, tag_id=tag.id, source_id=source_id)
-            )
+            .on_conflict_do_nothing(index_elements=["scene_id", "tag_id"])
-        ).scalar_one_or_none()
+        )
-        if existing is None:
+        session.execute(stmt)
-            session.add(SceneTag(scene_id=scene_id, tag_id=tag.id, source_id=source_id))
 
 
 def _sync_fingerprints(